From a0309faf1cb0622cac7c820150b7abf2024acff5 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 25 Apr 2025 17:11:07 -0700 Subject: [PATCH] mm: vmalloc: support more granular vrealloc() sizing Introduce struct vm_struct::requested_size so that the requested (re)allocation size is retained separately from the allocated area size. This means that KASAN will correctly poison the correct spans of requested bytes. This also means we can support growing the usable portion of an allocation that can already be supported by the existing area's existing allocation. Link: https://lkml.kernel.org/r/20250426001105.it.679-kees@kernel.org Fixes: 3ddc2fefe6f3 ("mm: vmalloc: implement vrealloc()") Signed-off-by: Kees Cook Reported-by: Erhard Furtner Closes: https://lore.kernel.org/all/20250408192503.6149a816@outsider.home/ Reviewed-by: Danilo Krummrich Cc: Michal Hocko Cc: "Uladzislau Rezki (Sony)" Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- include/linux/vmalloc.h | 1 + mm/vmalloc.c | 31 ++++++++++++++++++++++++------- 2 files changed, 25 insertions(+), 7 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 31e9ffd936e39..5ca8d4dd149d4 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -61,6 +61,7 @@ struct vm_struct { unsigned int nr_pages; phys_addr_t phys_addr; const void *caller; + unsigned long requested_size; }; struct vmap_area { diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ecd..2d7511654831e 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1940,7 +1940,7 @@ static inline void setup_vmalloc_vm(struct vm_struct *vm, { vm->flags = flags; vm->addr = (void *)va->va_start; - vm->size = va_size(va); + vm->size = vm->requested_size = va_size(va); vm->caller = caller; va->vm = vm; } @@ -3133,6 +3133,7 @@ struct vm_struct *__get_vm_area_node(unsigned long size, area->flags = flags; area->caller = caller; + area->requested_size = requested_size; va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area); if (IS_ERR(va)) { @@ -4063,6 +4064,8 @@ EXPORT_SYMBOL(vzalloc_node_noprof); */ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) { + struct vm_struct *vm = NULL; + size_t alloced_size = 0; size_t old_size = 0; void *n; @@ -4072,15 +4075,17 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) } if (p) { - struct vm_struct *vm; - vm = find_vm_area(p); if (unlikely(!vm)) { WARN(1, "Trying to vrealloc() nonexistent vm area (%p)\n", p); return NULL; } - old_size = get_vm_area_size(vm); + alloced_size = get_vm_area_size(vm); + old_size = vm->requested_size; + if (WARN(alloced_size < old_size, + "vrealloc() has mismatched area vs requested sizes (%p)\n", p)) + return NULL; } /* @@ -4088,14 +4093,26 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) * would be a good heuristic for when to shrink the vm_area? */ if (size <= old_size) { - /* Zero out spare memory. */ - if (want_init_on_alloc(flags)) + /* Zero out "freed" memory. */ + if (want_init_on_free()) memset((void *)p + size, 0, old_size - size); + vm->requested_size = size; kasan_poison_vmalloc(p + size, old_size - size); - kasan_unpoison_vmalloc(p, size, KASAN_VMALLOC_PROT_NORMAL); return (void *)p; } + /* + * We already have the bytes available in the allocation; use them. + */ + if (size <= alloced_size) { + kasan_unpoison_vmalloc(p + old_size, size - old_size, + KASAN_VMALLOC_PROT_NORMAL); + /* Zero out "alloced" memory. */ + if (want_init_on_alloc(flags)) + memset((void *)p + old_size, 0, size - old_size); + vm->requested_size = size; + } + /* TODO: Grow the vm_area, i.e. allocate and map additional pages. */ n = __vmalloc_noprof(size, flags); if (!n)